The present invention relates to a M-ary FSK receiver and to a method of demodulating a M-ary FSK modulated signal. Such receivers are used in communications receivers, such as paging receivers for POCSAG and ERMES which use M-ary FSK modulations.
In such receivers, an input signal is frequency down-converted to an IF which is passed to a demodulator and detector. For low cost applications such as paging, a limiter-discriminator-integrator (LDI) is widely used for recovering information upon which symbol decisions are made. The LDI approach provides a robust and simple detection method for M-ary FSK modulations. However, there is a performance penalty to pay for the simplicity of the hardware, the bit error rate (BER) does not compete with that available from other receiver structures, such as matched filter or correlator based detection.